Unsure of STD...symptoms, but tests negative

[Nemo2]

Good morning, Doctor...I am seeking your help because I am worried about my sexual health. I am a 31 yo male and currently in a heterosexual relationship. My girlfriend and I have been having unprotected sex for the last 5 months. No issues, problems, etc. About 3 weeks ago on a business trip I had an one night stand with a woman, who now looking back on it gave me every reason to believe that she does this often. During this encounter in my hotel room, I placed my condom on and immediately took it off, because I decided I didn't want to cheat. After some coaxing from her, which was stroking my penis with her hand. I picked the same condom up off the floor and put it back on. We had intercourse for about 2 mins, no ejaculation on my part, and I told her that we couldn't continue. I pulled the condom off and asked her to leave. I laid on my bed for about 10 mins, she had quite a bit of secretions that were in my groin area and I believe that my penis could have been laying in them(secretions) as I laid on my bed. I then took a shower and called it a night, totally feeling guilty.
I return back home 2 days later and had unprotected sex with my girlfriend twice in two days. Two days later(4 days after encounter with woman on biz trip) I start feeling an irritating feeling(slight burning) at the tip of my penis as well as a frequency in urination. I get extremely worried and look for some type of discharge. Three days after that (7 days after encounter) I see what is a very slight yellowish discharge when I woke up in the morning. I go to an STD clinic and get tested for Ghonorrea and Chylamidia. The results had 3 days to come thru so they gave me a one time treatment. Started with an "A" I believe and they mixed it with water...tasted horrible.
The next day my symptoms immediately started to subside, until 2 days later when it appeared the irritation was returning(no discharge, though). During this time..ie after my visit to the clinic, I was having protected sex with my girlfriend(which she thought was unusual). I also was masturbating once or twice a day.
The test results came back negative on Ghonorrea and Chylamidia but the feelings have not completely subsided. I went back to the clinic(2 weeks after encounter) and told them I still had slight symptoms and they gave me a urine test, which came back negative.
Now I tend to feel slight irritation in the evening or at night...during the day everything seems to be okay down there, except maybe I am urinating maybe one time more a day than I usually do. There has not been any discharge from my penis since the treatment was given at the clinic.

My questions:
1.) What are the chances that I actually caught an STD from this "encounter" ie can a reused condom or a womans vaginal fluid on my inner groin transmit to me if my penis is laying on it? HIV, could that have been transferred to me as well if this woman was infected? Also, what do you think it was that caused the STD symptoms?

2.) My girlfriend told me a week before my business trip that she had been tested positive for UTI's in the past and was currently having symptoms of it and had yeast infections in the past. Is it possible she could have passed something to me bacterially? I read 15% of yeast infections can be passed from a woman to a man. Also, she says the symptoms have gone away because she has been drinking a lot of water.

3.) Is my masturbation aggravating the process of my body recovering?

4.) I still feel like something is not quite right because at night(and pretty much only at night) I have what feels like an irritating feeling(no discharge). Do you think I still have the STD?

5.) The 2 times I had unprotected sex with my girlfriend, I want to be honest with her but I'm not sure if I have given her anything and don't want to ruin the relationship unneccesarily. What are the chances of her being infected with something?

Thank you!

[auntiejessi]

I agree.  This might be something like yeast, etc, but it sounds as if your gf needs a trip to the doc, too.

AJ

[Dallasfan]

Your encounter was no risk, but if you continue to feel soreness with urination, your may want a good exam from your Doctor. Take care